2-Aryl-5-(perfluoroalkyl)pyrrole compounds are useful as insecticidal and acaricidal agents. In addition, those compounds are also useful for the preparation of other insecticidal and acaricidal agents. In particular, 2-aryl-5-(perfluoroalkyl)pyrrole compounds are key intermediates in the preparation of arylpyrrole compounds such as chlorfenapyr. Accordingly, there is an ongoing search to discover new methods for the preparation of 2-aryl-5-(perfluoroalkyl)pyrrole compounds.
U.S. Pat. No. 5,145,986 discloses that 2-aryl-5-(trifluoromethyl)pyrrole compounds may be prepared by reacting an N-(substituted benzyl)-2,2,2-trifluoroacetimidoyl chloride compound with an .alpha.-halo-.alpha.,.beta.-unsaturated nitrile, ester or nitro compound in the presence of a base. However, the process described in U.S. Pat. No. 5,145,986 is not entirely satisfactory because the required .alpha.-halo-.alpha.,.beta.-unsaturated nitrile, ester or nitro compound is prepared in a two step--halogenation/dehydrohalogenation--process.
U.S. Pat. Nos. 5,446,170 and 5,426,225 disclose that 2-aryl-5-(trifluoromethyl)pyrrole compounds may be obtained in several steps from the appropriate aldehyde. The processes described in U.S. Pat. Nos. 5,446,170 and 5,426,225 require the use of an aminonitrile intermediate which is obtained via the Strecker synthesis from the appropriate aldehyde. However, the use of the Strecker synthesis is not entirely satisfactory because of cyanide containing waste streams.
It is, therefore, an object of the present invention to provide a new process for the preparation of 2-aryl-5-(perfluoroalkyl)pyrrole compounds which avoids the use of (.alpha.-halo-.alpha.,.beta.-unsaturated nitrile, ester and nitro compounds and the Strecker synthesis.
It is also an object of this invention to provide a new process for the preparation of arylpyrrole compounds such as chlorfenapyr.
A further object of the present invention is to provide new intermediate compounds which are useful in the processes described hereinbelow.
Those and other objects of the present invention will become more apparent from the detailed description thereof set forth below.